1. Field of the Invention
This invention generally concerns a device for determination of the proper contrast between a background substratum and darker symbols printed thereon, and more specifically concerns a device to assure the proper contrast of a light background to dark symbol bars printed thereon for Universal Product Codes symbols during artwork preparation and production of packaging material which utilize the Universal Product Codes.
Statement of the Problem
In recent years, several new consumer marketing systems have been developed to provide, inter alia, computer-assisted item pricing and inventory management. One such system, currently utilized by the food and drug industry, uses Universal Product Codes (U.P.C.) symbols which are a series of light and dark bar-like symbols of varying width and which are printed on the package or wrapper of consumer goods. These symbols are machine-readable by utilizing a photosensitive scanner which is responsive to the variation in symbol width printed on the package. The coded symbols represent information regarding the product manufacturer and a description of that particular product.
When the coded symbols are "read" by the scanner, the information is "interpreted" by computer. The computer is generally programmed to provide pricing and inventory information regarding each product.
The Universal Product Code Council has set specifications for this machine-readable symbol in the U.P.C. Symbol Specification Manual. Producers of grocery and drug packaging materials are required to print the symbols to these specifications, and producers of the photosensitive scanners are required to produce machines which will read the symbols printed to these specifications.
One of the specifications of the U.P.C. Symbol Specification Manual gives the required color density for the dark bars or symbols as a function of the light background upon which they are printed. This is to ensure uniformity throughout the U.P.C. system as an improper contrast between the background and the printed symbols will prevent the scanner from obtaining an accurate signal. To provide this uniformity, the manual requires that all print contrast signal measurements are to be made using equipment equivalent to the Kidder Optical Character Tester, Model 082 with a Wratten 26 filter and a 0.008 inch aperture. This particular type of equipment is very expensive (costs range from $2,500.00 to $3,000.00) and is cumbersome to use. Therefore, a simple method and device for approximating the same contrast measurement was needed.